Multi-taxa colonisation along the foreland of a vanishing equatorial glacier

Abstract

Retreating glaciers, icons of climate change, release new potential habitats for both aquatic and terrestrial organisms. High-elevation species are threatened by tempera-ture increases and the upward migration of lowlands species. Improving our under-standing of successional processes after glacier retreat becomes urgent, especially in the tropics, where glacier shrinkage is particularly fast. We examined the successional pat-terns of aquatic invertebrates, ground beetles, terrestrial plants, soil eukaryotes (algae, invertebrates, plants) in an equatorial glacier foreland (Carihuairazo, Ecuador). Based on both taxonomical identication and eDNA metabarcoding, we analysed the eects of both environmental conditions and age of deglacierization on community composi-tion. Except for algae, diversity increased with time since deglacierization, especially among passive dispersers, suggesting that dispersal was a key driver structuring the glacier foreland succession. Spatial -diversity was mainly attributed to nestedness for aquatic invertebrates, terrestrial plants and soil algae, likely linked to low environmen-tal variability within the studied glacier foreland; and to turnover for soil invertebrates, suggesting competition exclusion at the oldest successional stage. Pioneer communi-ties were dominated by species exhibiting exible feeding strategies and high dispersal ability (mainly transported by wind), probably colonising from lower altitudes, or from the glacier in the case of algae. Overall, glacier foreland colonisation in the trop-ics exhibit common characteristics to higher latitudes. High-elevation species are nev-ertheless threatened, as the imminent extinction of many tropical glaciers will afect species associated to glacier-inuenced habitats but also prevent cold-adapted and hygrophilous species from using these habitats as refuges in a warming world.